Absolute Densities of N2(A3Σu +), N(4So), and N(2Do) in an Inductively Coupled Nitrogen Plasma Source

The absolute densities of N2(A 3Σu +), N(4 S o), and N(2 D o) in an inductively coupled nitrogen plasma source were measured by cavity-ringdown and vacuum–ultraviolet absorption spectroscopies. It was found that the densities of the above three active species were on the same order of 1017 m-3. We observed the decrease in N2(A 3Σu +) density with increasing discharge pressure, while N(4 S o) and N(2 D o) densities increased with discharge pressure. Although the estimation of loss frequency suggested the loss of N2(A 3Σu +) due to collisional quenching, it was difficult to identify the dominant loss process quantitatively on the basis of the absolute densities and relevant reaction rate coefficients.